I have the same P5N32-SLI 32 Deluxe mobo and tested some 1000mhz DDR2 ram on it after reading your post, it came up with the same result. Obviously its chipset is too old to support the new higher speed ram, using the precision tweaker to overclock the 800mhz ram could run it at a higher speed but results would be variable to different makes, it doesn't mean your 1000mhz ram will run at its designated speed because it is beyond the mobo's spec, Asus won't guarantee anything on this. Your new mobo's Nvidia 590 chipset is more powerful and newer design to work with the latest components, you should be happy with it. I picked the P5WDH Deluxe for my new combination because I prefer the Crossfire instead of the SLI which is too costly to take that advantage.